Ridiculous place to sit when training? (5)

I believe the answer is:

potty

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'ridiculous' is the definition.
Both the definition and answer are adjectives. Maybe you can see an association between them that I don't see?

I don't understand the rest of the clue.

Can you help me to learn more?

(Other definitions for potty that I've seen before include "Foolish" , "Bonkers" , "Mad" , "Where youngster goes" , "Crazy (colloq.)" .)

I've seen this clue in The Times.

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